The BLAST family of protein and DNA database search programs constitute one of the key services offered by the NCBI. These programs are currently run on NCBI servers about 70,000 times during a typical weekday. This project represents an ongoing effort to improve and extend the functionality of these programs. Efforts this year have focussed primarily on the rewriting of existing BLAST code for consistency, the removal of bugs introduced during rapid code development by multiple parties, the documentation of existing code, and the extention of composition-based statistics to nucleotide database search versions of BLAST. Other efforts have been directed at adapting BLAST code for testing the effectiveness of compositionally adjusted substitution matrices in the context of general-purpose database searches.